Project Summary As stated in the original scope of the project, improvements in early diagnosis and treatment for breast cancer in women have resulted in increased survivorship. An unintended consequence of increased survival, however, is that more women are living with the negative sequelae associated with cancer treatment, including decreased physical function. Exercise has been beneficial in arresting these sequelae, but adherence to exercise guidelines continues to be a challenge. As most breast cancer survivors are middle-aged and older, an alternative to standard exercise programming is to foster low intensity exercise program but there is little information about the potential benefits of low intensity programming. The overall purpose of this study is to assess the impact of a low intensity versus moderate intensity endurance exercise program on the physical function of breast cancer survivors. Our hypothesis is that participants in the low intensity exercise program will demonstrate similar physical functioning as participants in the moderate intensity exercise program. The Theory of Planned Behavior serves as the framework for the intervention. A convenience sample of 142 women, residents of Puerto Rico, age 50 or older, with a diagnosis of breast cancer (stage 0 thru III), who have received treatment for breast cancer (with or without adjuvant therapy) are randomly assigned to a low intensity or moderate intensity endurance intervention. Both interventions are home-based, have a duration of 6 months, with education and guidance provided at our facilities by physical therapists at each exercise session. An evaluator, blinded to group assignment, assesses participants at baseline and at the completion of the intervention. Primary outcome measures consist of physical functioning and health-related quality of life.